This research is an investigation of estrogen biosynthesis and the interrelationships between human development and estrogen. It aims also to develop a useful analytical method of clinical applicability. Our immediate objectives are: (1) to elucidate the steric, kinetic, and electronic mechanisms of aromatization by human aromatizing systems, (2) to elucidate pathway(s) through which polyhydroxylated estrogens of feto-placental origin are formed, (3) to isolate polar estrogens and their conjugates and study the mode of conjugation and excretion, and (4) to elucidate steroid conformations in order to further our understandings of endrocrine processes at the molecular level. The methods are synthesis of steroids with and without deuterium, tritium and carbon-14 lables at stereoselective and/or regiospecific positions, conformational analysis by X-ray crystallography and spectrocsopy, chemical and biochemical distribution analysis of isotopes, incubations with various enzyme preparations and tissue homogenates of combinations of regio- and stereoselectively labeled steroids, and analyses of the products, kinetics and dynamic intermediates. A neutral resin, steady state distribution machine and chromatographies are used for the isolation of estrogen conjugates.